Abstract Chlamydia trachomatis is the most commonly reported bacterial infection in the United States and in many other parts of the world. Because untreated infection in women causes long term problems with reproduction such as infertility and ectopic pregnancy, chlamydia has been the focus of public health control programs over the last two decades. Current antibiotic treatments have not halted the increased incidence and C. trachomatis infections now cost the US health system $4-6 billion per annum. Despite mathematical modelling highlighting that even a partially effective vaccine could reverse the increasing incidence of infection and that the medical and research fields agree that a vaccine will be required to control the current epidemic, a human chlamydial vaccine trial has not occurred in over 50 years. NanoBio Corporation has developed NanoStat? adjuvant technology, that allows for both intranasal and intramuscular vaccine administration, produce balanced humoral and cell-mediated immune responses and offers a protection from a challenge in number of studies that include RSV, pandemic influenza and pertussis. In addition to the balanced TH1/Th2 immune response NE01-adjuvanted vaccines elicit strong Th17 response and humoral immunity in several species including humans, against many different antigens when delivered intranasally. Using NanoStat? we have shown that intranasal (IN) immunization of mice with the chlamydial major outer membrane protein (MOMP) reduces the duration of infection and greatly reduces inflammatory oviduct damage following genital chlamydia infection. Additionally, intramuscular immunization with MOMP/NE02, demonstrated the efficacy of this vaccine in decreasing both infection and pathology in mouse model. Dr. Mahony has recently developed a novel and improved type III secretion (T3SS) based chlamydial vaccine antigen (BD584) that has yielded very promising results by reducing bacterial shedding by 90% and upper genital tract pathology by 85% which should be able to offer protection from multiple chlamydia serovars based on the highly conserved nature of the T3SS proteins. Furthermore, the C. trachomatis mouse model developed in Dr. Mahony?s laboratory recapitulates infections seen in humans with C. trachomatis and thus are more relevant for evaluating the efficacy of chlamydia vaccines, as compared to C. muridarum mouse models that are routinely used for chlamydia studies. The preliminary data support further evaluation of an NE-adjuvanted chlamydia vaccine to demonstrate protection against both infection and pathology. In this proposal, we will utilize this newly developed C. trachomatis mouse model and both intranasal and intramuscular applications of nanoemulsion-adjuvanted BD584 vaccine to further develop and demonstrate the importance of NanoStatTM in preventing chlamydial disease and establish proof-of-concept necessary to initiate human clinical trials of a chlamydia vaccine. This project will identify an effective vaccine composition/regiment and provide proof of concept data to seek SBIR Phase II funding to support further development of safe and efficacious chlamydia vaccine.